Individual Grounding rods

[siva]

Hi
In our building, we have various systems like Public address,Personal alert,Fire alarm,Cable TV etc.Contractor proposes individual earthing rods for these systems.ie these earth rods will not connected to the main Ground ring.Is this allowed as per NEC?

Thanks in advance
Siva

 

[dillon3c]

Re: Individual Grounding rods

Originally posted by siva:
Contractor proposes individual earthing rods for these systems.ie these earth rods will not connected to the main Ground ring.Is this allowed as per NEC?

please see..
810.21(f)Electrode.
800.100(b)(1)Building or Structure with Grounding Means.

 

[charlie tuna]

Re: Individual Grounding rods

siva,
under certain conditions this could be allowed depending on the building's existing construction. the normal buildings of today have grounding systems in place. all the systems you mentioned require a low resistance ground path back to their power source. a driven ground rod does not provide this. it has been my expirience that this type of installation (driven individual ground rods) causes problems by only providing a false sense of protection for these systems. in the many instances that we were called on for power monitoring -- we install a ground conductor back to the equipment's power source and remove the driven ground rod. this has always solved their problems!!!